Segment Reporting - Schedule of Company's Revenue and Income From Operations by Segment (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information [Line Items]
Revenues	$ 104,621	$ 126,401	$ 409,192	$ 345,207
Voyage expenses	(14,933)	(2,653)	(37,514)	(10,164)
Vessel operating expenses	(44,783)	(35,267)	(136,245)	(87,085)
Time-charter hire expense	(11,335)	(21,382)	(47,964)	(53,178)
Depreciation and amortization	(25,888)	(17,878)	(78,576)	(48,346)
General and administrative expenses	(3,572)	(4,310)	(13,774)	(10,992)
Asset impairments	(7,766)	0	(14,186)	0
Loss on sale of vessel	(137)	0	(137)	0
Restructuring charges	0	(327)	0	(4,772)
(Loss) income from operations	(3,793)	44,584	80,796	130,670
Equity Income	1,045	2,762	9,599	8,931
Operating Segments [Member] \| Conventional Tankers [Member]
Segment Reporting Information [Line Items]
Revenues	95,626	117,863	380,283	336,669
Voyage expenses	(15,775)	(2,461)	(39,527)	(9,972)
Vessel operating expenses	(37,462)	(29,164)	(112,248)	(80,982)
Time-charter hire expense	(10,784)	(21,344)	(46,670)	(53,140)
Depreciation and amortization	(24,651)	(17,234)	(74,925)	(47,702)
General and administrative expenses	(2,955)	(3,398)	(11,359)	(10,080)
Asset impairments	(7,766)		(14,186)
Loss on sale of vessel	(137)		(137)
Restructuring charges		0		(4,445)
(Loss) income from operations	(3,904)	44,262	81,231	130,348
Equity Income	1,045	2,762	9,599	8,931
Operating Segments [Member] \| Ship-to-Ship Transfer [Member]
Segment Reporting Information [Line Items]
Revenues	9,837	8,850	30,922	8,850
Voyage expenses	0	(192)	0	(192)
Vessel operating expenses	(7,321)	(6,415)	(23,997)	(6,415)
Time-charter hire expense	(551)	(38)	(1,294)	(38)
Depreciation and amortization	(1,237)	(644)	(3,651)	(644)
General and administrative expenses	(617)	(912)	(2,415)	(912)
Asset impairments	0		0
Loss on sale of vessel	0		0
Restructuring charges		(327)		(327)
(Loss) income from operations	111	322	(435)	322
Equity Income	0	0	0	0
Inter-segment Revenue [Member]
Segment Reporting Information [Line Items]
Revenues	(842)	(312)	(2,013)	(312)
Voyage expenses	842	0	2,013	0
Vessel operating expenses	0	312	0	312
Time-charter hire expense	0	0	0	0
Depreciation and amortization	0	0	0	0
General and administrative expenses	0	0	0	0
Asset impairments	0		0
Loss on sale of vessel	0		0
Restructuring charges		0		0
(Loss) income from operations	0	0	0	0
Equity Income	0	0	0	0
Lightering support services, cost per voyage	$ 25	$ 25	$ 25	$ 25

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Lightering Support Services, Cost per Voyage

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Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

+ References

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-Publisher FASB
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Total costs related to services rendered by an entity during the reporting period.

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The current period expense charged against earnings on long-lived, physical assets not used in production, and which are not intended for resale, to allocate or recognize the cost of such assets over their useful lives; or to record the reduction in book value of an intangible asset over the benefit period of such asset; or to reflect consumption during the period of an asset that is not used in production.

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The aggregate direct operating costs incurred during the reporting period.

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Amount of gain (loss) on sale or disposal of property, plant and equipment assets, including oil and gas property and timber property.

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This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

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- Definition

Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

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The net result for the period of deducting operating expenses from operating revenues.

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Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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